Modern automotive vehicles have an on-board diagnostics (“OBD”) port coupled to one or more data communication buses of the vehicle, which are typically controller area network (“CAN”) buses. As is known in the art, CAN is a multi-master serial bus standard for connecting electronic devices, typically electronic control units (“ECUs”), which are also known as nodes. In servicing such vehicles, a diagnostic tool is coupled to the OBD port and is used to read out diagnostic codes from the vehicles. In some cases, the diagnostic tool also runs diagnostic routines and/or causes an electronic control unit or other electronic device to run self-diagnostic routines. Since the OBD port is coupled to the CAN bus (or buses) of the vehicle over which electronic devices in the vehicle communicate with each other, the OBD port could be used by a hacker to hack electronic devices in the vehicle, such as altering their programming in an improper manner, introduce malware onto the vehicle, or otherwise compromise security of electronic devices in the vehicle.